Base exchange material and method of preparing same



method, as distinguished from Patented Apr. 29, 1930 UNITED STATESPATENT OFFICE no Drawing. Application filed April 24,

This invention relates to the preparation of zeolites or base exchangematerials and in particular to the preparation of such materials by whatis known generally as the wet baking, sintering or fusing the componentconstituents. The invention may further be classified as an improvementin the preparation of base exchange materials in which sodium aluminateand silicic acid, or their equivalents, are employed.

It has long been known that substances resembling zeolites in chemicalcomposition, characteristics and action could be formed by the reactionof sodium aluminate on hydrated silica. But according to the methodsheretofore proposed for the formation of such substances, the endproduct obtained was poorly ada ted for technical use because of theunsatis actory and unstable physical condition of the materials.

The object of this invention is to provide a method for treating silicicacid, or silicic acid gel, with sodium aluminate, or equivalent alkalinesolutions of amphoteric hydroxides, for the production of base exchangematerials whic. shall have the proper chemical and physicalcharacteristics requisite for presentday industrial practice,and toeffect economies in procedure accompanied by ease and convenience inoperation and handlin In attainment of the object of the invention Iprefer to employ silicic acid, in colloidal solution, which mayconveniently be prepared by adding to the solution of an alkali metalsilicate, an amount of acid in excess of that required to neutralize thetotal alkalinity of the silicate. In the optional procedure, silicicacid gel may be prepared by partiall or completely neutralizing asolution of an a kali metal silicate. The gel may be moist or undriedwhen subjected to'react-ionwith the solution of sodium aluminate, or itmay have been dried and so used either with or without previous washingto remove soluble compounds.

In the preferred method of preparation, a colloidal solution of silicicacid, prepared as above, is treated with a solution of sodium aluminate,using such proportion and con- 1924. Serial No. 708,671.

centration of the reagents, that the resulting gel embraces the entirereaction volume without subsequent separation of mother liquor. Upon drmg, the mass breaks into small hard lumps w ich granulate when wetted.These granules are of suitable size for employment in the softening ofwater in the well known way, butthey may be made smaller by crushing tosuit a particular requirement.

A specific example of the preferred procedure according to the inventionis as follows: 6 liters of commercial sodium silicate solution, e0 Baumcontaining about 9% Na Oand 28.5% SiO is diluted to liters. To this isadded 14 liters of dilute sul huric acid containing about 112 grams H 84 per liter and thoroughly mixed. The colloidal solution of silicic acidresulting, will remain aluminate'containing about 20 grams Na O and 14grams A1 0 per liter. In these proportions, the mixture will be alkalineto phenolphthalein. It is preferable that prior to mixing both solutionsbe cooled to about 5 C., hich case the mixture remains fluid for about aminute, after which, it gradually sets to a. stiff, firm gel embracingall of the reaction volume. The gel is dried at a temperature u der 1000., preferably at about U on drying, the mass breaks into small, hardlumps which in subsequent wetting are resolved into hard, vitreousgranules, having a density of from to pounds per cubic foot, and anexchange capacity of about 250 grains calcium carbonate equivalent perpound.

Where silicic acid or silicic acid gel is used I prefer to employparticles of dried gel about the size desired in the final product. Suchparticles are boiled for two hours in a solution of sodium aluminate,containing about 3 grams Na O and 2.2 grams A1 0 per liter andthereafter for two hours in a so lution of the same character but twiceas strong. The particles are then washed to remove excess solution anddried, when they are ready for use in the softening of water. Theseparticles are hard, strong and resistive to the powdering action ofwater, they and 1n the times and temperatures for treatpossess a highbase exchange capacity and are otherwise suitable for technical use.

These illustrations of the application of the principles of theinvention by no means embrace all of the possibilities for improvementover the prior practices as obviously the invention is susceptible ofemployment within a wide range of equivalents utilizing variations andmodifications in the strength, roportions and composition of thereagents ment.

In the preferred example cited it is not absolutely essential that allof the constituent elements of the reagents be embraced in the gelalthough I consider that it is conducive of better results to employsolutions of a degree of concentration which will bring about thatresult.

The chemical composition of the final product may be altered toadvantage for certain purposes by increasing the silica contentaccording to the disclosure of my copending application Serial No. 700,822, filed March 21, 1924:. Also a very satisfactory material may beproduced by varying the proportions of the reagents so that the mixtureis neutral to phenolphthalein or litmus but alkaline to methyl orange.

Other modifications in procedure, variations in constituents andadditions in refinement of the product according to either example, willundoubtedly occur to those skilled in the art as a result of thedisclosure herein, and be based upon the underlying principles of theinvention as defined in the appended claims.

The word amphoterate in the claims includes the salts of the acids ofthe amphoteric metals such as the aluminates.

I claim:

1. The processfifpreparing base exchange materials which coinprisestreating colloidal solution, of silicic acid with an alkali metalaluminate.

2. The process of preparing base exchange materials which comprisestreating colloidal materials which solution of silicic acid with analkali metal aluminate and removing all the moisture.

The process of preparing base exchange materials which comprisestreating a colloidal solution of silicic acid with a solution of analkali metal aluminate, removing the moisture and dividing'the mass intosmall particles suitable for use in the softening of water.

4. The process of preparing base exchange comprises mixing a coolecolloidal solution of silicic acid with a cooled solution of sodiumaluminate to form a gel, drying the gel and then wetting it to reduce itto small particles.

5. The process of preparing ametallo-sihcate which comprises treating asolutlon of sodium silicate with an acid, then subjecting it to theaction of a solution of-sodium aluminate, and drying the resulting gel.

6. The process of preparing base exchange materials which comprisestreating a colloidal solution of silicic acid with a solution of analkali metal aluminate, drying the resulting gel and then wetting it.

7. The process of preparing base exchange materials which comprisessolution of silicic acid with a solution of an alkali metal aluminate insuch proportion and degree of concentration that a firm stiff gel isformed embracing the entire reaction volume, and drying the gel.

8. The process of preparing a metallo-silicate which comprises treatinga solution of sodium silicate with sulphuric acid, then subjecting it tothe action of sodium aluminate, drying the resulting gel and thenwetting it to form hard vitreous particles suitable for use in thesoftening of water.

9. The process of preparing a metallo-silicate which comprises treatinga solution of sodium silicate with a quantity of acid in excess of thatrequired to neutralize the total alkalinity, then mixing it with asolution of SO(1lll.lm aluminate and drying the resulting 10. Theprocess of preparing a metallosilicate which comprises treating analkali metal silicate with a quantity of acid in excess of that requiredto neutralize the total alkalinity, then mixing it with a solution of analkali metal amphoterate and drying the resulting gel.

11. A metallo-silicate substantially identical with the precipitate ofmixed solutions of colloidal silicic acid and alkali metal aluminate.

12. The process of preparing base exchange materials which comprisesproviding a colloidal solution of silicic acid, providing an alkalinesolution of an amphoteric hydroxide and mixing the two solutions.

13. The process of preparing base exchange materials which comprisesproviding a suspension of colloidally dispersed particles of hydratedsilica and mixing this suspension with an alkaline solution of anamphoteric hydroxide.

14. The process of preparing base exchange materials which comprisesmixing a colloidal solution of silicic acid with an alkaline solution ofan amphoteric hydroxide, a substantially larger volume of the colloidalsolution of silicic acid being used than the volume of the alkalinesolution of the amphoteric d hydroxide.

15. The process of preparing base exchange materials which comprisesadding a colloidal solution of silicic acid to an alkaline solution ofan amphoteric hydroxide.

In testimony whereof I have hereunto subscribed my name.

ABRAHAM S. BEHRMAN.

mixing a colloidal

